Corrosion inhibitors containing cationic surfactants

ABSTRACT

The invention relates to the use of compositions containing metal salts of compounds of the formula (1) 
     
       
         
         
             
             
         
       
     
     in which R 1  is C 1 - to C 29 -alkyl, C 2 - to C 29 -alkenyl, C 6 - to C 30 -aryl or C 7 - to C 30 -alkylaryl, and cationic surfactants as corrosion inhibitors.

The present invention is described in the German priority application No. 10 2007 041 216.0 filed Aug. 31, 2007, which is hereby incorporated by reference as is fully disclosed herein.

The present invention relates to a process for corrosion inhibition on and in apparatuses for conveying and transporting hydrocarbons in oil production and processing by adding a metal salt of N-acylmethionine and a cationic surfactant to the corrosive system.

In industrial processes in which metals come into contact with water or with oil/water two-phase systems, there is the danger of corrosion. This is particularly pronounced if the aqueous phase has a high salt content, as in oil extraction and processing processors, or is acidic due to dissolved acid gases, such as carbon dioxide or hydrogen sulfide. The exploitation of a deposit and the processing of oil are therefore not possible without special additives for protecting the equipment used.

Although suitable corrosion inhibitors for oil production and processing have long been known, they are often insufficiently effective at a low dose.

As typical corrosion inhibitors of the prior art, amides, amidoamines or imidazolines of fatty acids and polyamines have an extremely good oil solubility and, owing to poor partitioning, are therefore present only in low concentration in the corrosive water phase. Accordingly, these products must be used at a high dose for an optimal effect.

Quaternary alkylammonium compounds (quats) are alternative corrosion inhibitors of the prior art, which also have biostatic properties in addition to the corrosion-inhibiting properties. In spite of improved water solubility, the quats have a substantially

reduced film persistence, for example compared with the imidazolines, and therefore likewise lead to effective corrosion protection only in relatively high doses.

U.S. Pat. No. 4,240,823 describes N-acylmethionine derivatives which are used as growth regulators in the area of crop protection.

JP-A-8 337 562 and JP-A-8 337 563 describe N-acylamino acids and their alkali metal salts, which can also be used as corrosion inhibitors.

JP-A-49 026 145 describes alkali metal salts of N-acylamino acids, which salts can be used as corrosion inhibitors. N-lauroylglycine sodium salt is mentioned as an example.

A disadvantage of the compounds of the prior art is, however, that their activity is not sufficient and that they have a strong tendency to foam.

It was an object of the present invention to provide novel corrosion inhibitors which, in combination with improved corrosion protection, also afford less foaming in comparison with the corrosion inhibitors of the prior art.

It has now surprisingly been found that metal salts of N-acylmethionine as a mixture with cationic surfactants have an excellent effect as corrosion inhibitors and have very little tendency to foam formation.

The invention therefore relates to the use of compositions containing metal salts of compounds of the formula (1)

-   -   in which R¹ is C₁- to C₂₉-alkyl, C₂- to C₂₉-alkenyl, C₆- to         C₃₀-aryl or C₇- to C₃₀-alkylaryl, and cationic surfactants as         corrosion inhibitors.

The invention furthermore relates to a process for inhibiting corrosion on metal surfaces, in particular of iron-containing metals, by adding at least one metal salt of compounds of the formula (1) and a cationic surfactant to a corrosive system which is in contact with the metal surfaces.

The invention furthermore relates to compositions containing at least one metal salt of a compound of the formula (1) and at least one cationic surfactant.

The invention furthermore relates to the use of metal salts of compounds of the formula (1) together with cationic surfactants as metal processing compositions. Here, the compositions according to the invention also afford very good corrosion protection even under strong mechanical load, such as during grinding, cutting and drilling of metal workpieces.

Corrosive systems in the context of this invention are preferably liquid/liquid or liquid/gaseous multiphase systems consisting of water and hydrocarbons which contain corrosive constituents, such as salts and acids, in free and/or dissolved form. The corrosive constituents may also be gaseous, such as, for example, hydrogen sulfide and carbon dioxide.

Hydrocarbons in the context of this invention are organic compounds which are constituents of mineral oil/natural gas, and the secondary products thereof. Hydrocarbons in the context of this invention are also readily volatile hydrocarbons, such as, for example, methane, ethane, propane and butane. For the purposes of this invention, these also include the further gaseous constituents of mineral oil/natural gas, such as, for example, hydrogen sulfide and carbon dioxide.

Preferred surfactants are those which, in a concentration of 0.5% by weight in water, produce a surface tension of this aqueous solution of not more than 55 mN/m, particularly preferably of not more than 50 mN/m and especially not more than 45 mN/m.

In a further preferred embodiment of the invention, R¹ is C₃- to C₂₃-alkyl, C₃- to C₂-alkenyl, C₆- to C₂₄-aryl or C₇- to C₂₅-alkylaryl, in particular an alkyl or alkenyl group having 7 to 17 carbon atoms.

Suitable cationic surfactants are described below.

Suitable cationic surfactants are preferably present as chlorides or bromides but may also be used in the form of methosulfates.

Suitable cationic surfactants are, for example, quaternary ammonium salts, such as di(C₈-C₂₄)-alkyldimethylammonium chloride or bromide, preferably di(C₁₂-C₁₈)-alkyl-dimethylammonium chloride or bromide, e.g. distearyidimethylammonium chloride or bromide, di-tallow-alkyldimethylammonium chloride or bromide, dioleyldimethylammonium chloride or bromide, dicocoalkyldimethylammonium chloride or bromide; (C₈-C₂₄)-alkyldimethylethylammonium chloride or bromide; (C₈-C₂₄)-alkyltrimethylammonium chloride or bromide, preferably cetyltrimethylammonium chloride or bromide and (C₂₀-C₂₂)-alkyltrimethylammonium chloride or bromide; (C₈-C₂₄)-alkyl-dimethylbenzylammonium chloride or bromide, preferably (C₁₂-C₁₈)-alkyldimethyl-benzylammonium chloride; N—(C₁₀-C₁₈)-alkylpyridinium chloride or bromide, preferably N—(C₁₂-C₁₆)-alkylpyridinium chloride or bromide; N—(C₁₀-C₁₈)-alkylisoquinolinium chloride, bromide or monoalkylsulfate; N—(C₁₂-C₁₈)-alkyl-polyoylaminoformylmethylpyridinium chloride; N—(C₁₂-C₁₈)-alkyl-N-methylmorpholinium chloride, bromide or monoalkylsulfate; N—(C₁₂-C₁₈)-alkyl-N-ethylmorpholinium chloride, bromide or monoalkylsulfate; (C₁₆-C₁₈)-alkylpentaoxyethylammonium chloride; diisobutylphenoxyethoxyethyldimethylbenzylammonium chloride; salts of N,N-diethylaminoethylstearylamide and -oleylamide with hydrochloric acid, acetic acid, lactic acid, citric acid or phosphoric acid; N-acylaminoethyl-N,N-diethyl-N-methylammonium chloride, bromide or monoalkylsulfate and N-acylaminoethyl-N,N-diethyl-N-benzylammonium chloride, bromide or monoalkylsulfate, acyl preferably being stearyl or oleyl.

A particularly preferred class of cationic surfactants comprise the so-called ester quats, e.g. the triethanolamine diester quat and the diethanolmethylamine diester quat. These are prepared starting from amino alcohols, such as triethanolamine or diethanolmethylamine, by esterifying the amino alcohols with from one to two (in the case of triethanolamine up to three), preferably with two mol of a fatty acid and subsequently quaternizing them with a methylating agent such as methyl chloride, methyl bromide or dimethylsulfate. C₈-C₂₄-fatty acids, which may be saturated or unsaturated, such as, for example, stearic acid, tallow fatty acid (including partly hydrogenated), coconut fatty acid, behenic acid and oleic acid, are used as fatty acids for esterifying C₈-C₂₄ fatty acids.

Further preferred cationic surfactants are alkylhydroxyethylammonium salts according to the formula (2)

-   -   in which R1 is a linear or branched, saturated or unsaturated         alkyl group having 5 to 22 carbon atoms, preferably 8 to 18         carbon atoms, particularly preferably 12 to 14 carbon atoms, R2         is a methyl group, R3 is a methyl group or a group of the         formula -A-(OA)_(n)-OH, it being possible for A to be a —C₂H₄         and/or —C₃H₆ group and n to be a number from 0 to 20, R4 is a         group of the formula -A-(OA)_(n)-OH and X is an anion. X is, for         example, chloride, bromide, iodide, fluoride, sulfate, hydrogen         sulfate, carbonate, bicarbonate, acetate, citrate, phosphate,         mono- and dihydrogen phosphate, pyrophosphate, polyphosphate,         metaphosphate, nitrate, methylsulfate, phosphonate,         methylphosphonate, methanedisulfonate, methanesulfonate,         ethanesulfonate or an anion of the formulae R6SO₃, R7SO₄ or         R6COO, in which R6 and R7 are C₂-C₂₀-alkyl, preferably         C₁₀-C₁₈-alkyl, and R7 is additionally C₁-C₁₈-alkylphenyl.

Quaternary C₁₂-C₁₄-alkyldimethylhydroxyethylammonium chloride or methosulfate is particularly preferred as a compound of the formula (2).

Further preferred cationic surfactants are imidazoline quats or salts of the formulae (3) to (5):

-   -   in which R is an alkyl, alkenyl or alkylaryl group having 4 to         22 carbon atoms, R1 is a hydrogen atom or an alkyl or         hydroxyalkyl group having 1 to 3 carbon atoms, n is a number         from 0 to 10 and X is an anion. X is, for example, chloride,         bromide, sulfate, hydrogen sulfate, acetate or methylsulfate,         but may also have the meanings stated for X in formula 2.

For particularly preferred compounds of the formulae (3) to (5), R is C₇-C₁₇-alkyl or alkenyl, R1 is H or CH₃, n is from 1 to 4 and X is Cl or acetate.

In aqueous formulations, imidazolinium compounds of the formulae (3) to (5) tend to hydrolyze to the corresponding amidoamine compounds, which can likewise be used according to the invention.

The compositions according to the invention can be used alone or in combination with other known corrosion inhibitors. In general, the composition according to the invention is used in an amount such that sufficient corrosion protection is obtained under the given conditions.

Preferred concentrations in which the compositions according to the invention are used are from 5 to 5000 ppm, preferably from 10 to 1000 ppm, in particular from 15 to 150 ppm. The mixing ratio between metal salt of the compound 1 and cationic surfactant is preferably from 1:9 to 9:1, in particular from 3:7 to 7:3.

Mixtures of the compositions according to the invention with other corrosion inhibitors of the prior art are also particularly suitable as corrosion inhibitors.

EXAMPLES

General method for the preparation of metal salts of N-acylmethionine

In a standard stirred apparatus, 1 mol of DL-methionine in 300 ml of water are neutralized with 50% strength aqueous metal hydroxide solution. 1 mol of carboxylic acid chloride is metered into the resulting solution at 15-20° C., the pH being kept at 10-13 by simultaneous metering of 15% strength aqueous metal hydroxide solution. The reaction solution is stirred for a further 3 h at room temperature. The resulting metal salt of N-acylmethionine is characterized by means of the alkali number (AN) and active substance content. Stated percentages are percentages by weight, based on the weight of the salt according to the invention.

Example 1 N-Cocoyl-DL-methionine sodium salt (comparison)

N-Cocoyl-DL-methionine sodium salt having an active substance content of 40% and an AN=65 mg KOH/g was obtained from coconut fatty acid chloride, DL-methionine and sodium hydroxide.

Example 2 N-Oleoyl-DL-methionine potassium salt (comparison)

N-Oleoyl-DL-methionine potassium salt having an active substance content of 40% and an AN=56 mg KOH/g was obtained from oleoyl chloride, DL-methionine and potassium hydroxide.

Example 3 Corrosion Inhibitor Mixture 1

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 40 g of a 20% strength aqueous solution of cetyltrimethylammonium chloride and 20 g of butylglycol.

Example 4 Corrosion Inhibitor Mixture 2

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 8 g of dicocoalkyldimethylammonium chloride, 20 g of butylglycol and 32 g of water.

Example 5 Corrosion Inhibitor Mixture 3

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 40 g of a 20% strength aqueous solution of C₁₂-C₁₈-alkyldimethylbenzylammonium bromide and 20 g of butylglycol.

Example 6 Corrosion Inhibitor Mixture 4

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 8 g of triethanolammonium(dioleyl ester)methosulfate, 20 g of butylglycol and 32 g of water.

Example 7 Corrosion Inhibitor Mixture 5

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 8 g of C₁₂-C₁₄-alkyldimethylhydroxyethylammonium methosulfate, 20 g of butylglycol and 32 g of water.

Example 8 Corrosion Inhibitor Mixture 6

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 8 g of oleyl(hydroxyethyl)imidazolinium acetate, 20 g of butylglycol and 32 g of water.

Example 9 Corrosion Inhibitor Mixture 7

40 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 8 g of cocoyl(aminoethyl)methylimidazolinium chloride, 20 g of butylglycol and 32 g of water.

Example 10 Corrosion Inhibitor Mixture 8

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 40 g of a 20% strength aqueous solution of cetyltrimethylammonium chloride and 20 g of butylglycol.

Example 11 Corrosion Inhibitor Mixture 9

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 8 g of dicocoalkyldimethylammonium chloride, 20 g of butylglycol and 32 g of water.

Example 12 Corrosion Inhibitor Mixture 10

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 40 g of a 20% strength aqueous solution of C₁₂-C₁₈-alkyldimethylbenzylammonium bromide and 20 g of butylglycol.

Example 13 Corrosion inhibitor mixture 11

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 8 g of triethanolammonium(dioleyl ester)methosulfate, 20 g of butylglycol and 32 g of water.

Example 14 Corrosion Inhibitor Mixture 12

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 8 g of C₁₂-C₁₄-alkyldimethylhydroxyethylammonium methosulfate, 20 g of butylglycol and 32 g of water.

Example 15 Corrosion Inhibitor Mixture 13

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 8 g of oleyl(hydroxyethyl)imidazolinium acetate, 20 g of butylglycol and 32 g of water.

Example 16 Corrosion Inhibitor Mixture 14

40 g of N-oleoyl-DL-methionine potassium salt from example 2 were mixed with 8 g of cocoyl(aminoethyl)methylimidazolinium chloride, 20 g of butylglycol and 32 g of water.

Example 17 Corrosion Inhibitor Mixture 15

55 g of N-cocoyl-DL-methionine sodium salt from example 1 were mixed with 2 g of oleyl(hydroxyethyl)imidazolinium acetate, 20 g of butylglycol and 23 g of water.

Activity of the compounds according to the invention as corrosion inhibitors

The compounds according to the invention were tested as corrosion inhibitors in the Shell wheel test. Coupons of C steel (DIN 1.1203 with 15 cm² surface area) were immersed in a salt water/petroleum mixture (9:1,5% strength NaCl solution adjusted to pH 3.5 with acetic acid) and exposed to this medium at a speed of 40 rpm at 70° C. for 24 hours. The inhibitor dose was 50 ppm of a 24% solution of the inhibitor. The protection values were calculated from the decrease in the mass of the coupons, based on a blank value.

In the following tables, “comparison 1” designates a commercially available residue amine quat based on dicocosalkyl dimethylammonium chloride, “comparison 2” a commercially available imidazoline salt based on oleic acid diethylenetriamine and “comparison 3” an example from DE-10 2006 002 784 (morpholinium salt of N-cocoyl-DL-methionine, corrosion inhibitor of the prior art).

TABLE 1 (Shell wheel test) Example Corrosion inhibitor ø protection % Comparison 1 Standard quat 28 Comparison 2 Oleic acid DETA imidazoline 70 Comparison 3 Morpholinium salt of N-cocoyl-DL- 75 methionine Comparison 4 from example 1 67 Comparison 5 from example 2 69 18 from example 3 83 19 from example 4 80 20 from example 5 86 21 from example 6 86 22 from example 7 85 23 from example 8 93 24 from example 9 94 25 from example 10 87 26 from example 11 86 27 from example 12 85 28 from example 13 85 29 from example 14 89 30 from example 15 95 31 from example 16 95 32 from example 17 80

As is evident from table 1, the compositions according to the invention have very good corrosion inhibition properties at a very low dose and in some cases even substantially surpass the activity of the inhibitors of the prior art.

In comparison with example 23, example 32 shows that the synergistic effect of the metal salt of N-acylmethionine in combination with a cationic surfactant decreases at a ratio of >9:1 but is still present.

TABLE 2 (shaking foam test): The foam properties were tested by the shaking foam method. For this purpose, 50 ml of a 3% strength aqueous solution of the corresponding corrosion inhibitor in demineralized water were shaken 20 times in a closed 100 ml measuring cylinder in the course of 10 seconds. After the end of the shaking, the total volume of the solution (foam height) and the foam disintegration time (time before the starting volume of 50 ml is reached) were used for assessing the foam behavior. In general, this test method is reasonably reproducible but is outstandingly suitable for estimating the tendency of the foam behavior to be weakly foaming, foaming or strongly foaming. Example Corrosion inhibitor Foam behavior Comparison 1 Standard quat strongly foaming Comparison 2 Oleic acid-DETA-imidazoline strongly foaming Comparison 3 N-cocoyl-DL-methionine- foaming morpholinium salt Comparison 4 from example 1 foaming Comparison 5 from example 2 foaming 18 from example 3 weakly foaming 19 from example 4 weakly foaming 20 from example 5 weakly foaming 21 from example 6 weakly foaming 22 from example 7 weakly foaming 23 from example 8 weakly foaming 24 from example 9 weakly foaming 25 from example 10 weakly foaming 26 from example 11 weakly foaming 27 from example 12 weakly foaming 28 from example 13 weakly foaming 29 from example 14 weakly foaming 30 from example 15 weakly foaming 31 from example 16 weakly foaming 32 from example 17 weakly foaming

Table 2 shows that the compounds according to the invention have a substantially lower tendency to foam formation than the compounds from the prior art. 

1. The use of compositions containing metal salts of compounds of the formula (1)

in which R′ is C₁- to C₂₉-alkyl, C₂- to C₂₉-alkenyl, C₆- to C₃₀-aryl or C₇- to C₃₀-akylaryl, and cationic surfactants as corrosion inhibitors.
 2. The use as claimed in claim 1, R′ being an alkyl or alkenyl group having 7 to 17 carbon atoms.
 3. The use as claimed in claim 1 and/or 2, the metal salt being an alkali metal salt.
 4. The use as claimed in one or more of claims 1 to 3, the cationic surfactant being a quaternary ammonium salt which contains at least one C₈- to C₂₄-alkyl or alkenyl group linked to the nitrogen atom of the ammonium group.
 5. The use as claimed in one or more of claims 1 to 4, the cationic surfactant being an ester quat which is obtainable by esterification of an amino alcohol with a C₈- to C₂₄-fatty acid and subsequent quaternization of the amino groups with a methylating agent.
 6. The use as claimed in one or more of claims 1 to 5, the cationic surfactant corresponding to the formula (2)

in which R1 is C₅- to C₂₂-alkyl R2 is methyl R3 is methyl or -A-(OA)_(n)-OH R4 is -A-(OA)_(n)-OH A is —C₂H₄— n is a number from 0 to 20 X is a suitable anion.
 7. The use as claimed in one or more of claims 1 to 6, the cationic surfactant corresponding to the formulae (3) to (5)

in which R is C₄- to C₂₂-alkyl, C₄- to C₂₂-alkenyl or C₄- to C₂₂-alkylaryl R1 is H, C₁- to C₃-alkyl or C₂- to C₃-hydroxyalkyl n is a number from 0 to 10 X is a suitable anion.
 8. The use as claimed in claim 6 or 7, wherein X is an anion selected from chloride, bromide, iodide, fluoride, sulfate, hydrogen sulfate, carbonate, bicarbonate, acetate, citrate, phosphate, mono- and dihydrogen phosphate, pyrophosphate, polyphosphate, metaphosphate, nitrate, methylsulfate, phosphonate, methylphosphonate, methanedisulfonate, methylsulfonate, ethanesulfonate or an anion of the formulae R⁶SO₃, R⁷SO₄ or R⁶COO, in which R⁶ and R⁷ are C₂-C₂₀-alkyl, preferably C₁₀-C₁₈-alkyl, and R⁷ is additionally C₁-C₁₈-alkylphenyl.
 9. The use as claimed in one or more of claims 1 to 8, wherein the total amount of metal salt to cationic surfactant is from 5 to 5000 ppm.
 10. The use as claimed in one or more of claims 1 to 9, wherein the weight ratio of metal salt to cationic surfactant is from 1:9 to 9:1.
 11. The use as claimed in one or more of claims 1 to 10 as corrosion inhibitors in apparatuses for conveying and transporting hydrocarbons in oil production and processing.
 12. The use as claimed in one or more of claims 1 to 11 as corrosion inhibitors in metal processing compositions.
 13. A composition containing at least one metal salt of a compound of the formula (1)

in which R′ is C₁- to C₂₉-alkyl, C₂- to C₂₉-alkenyl, C₆- to C₃₀-aryl or C₇- to C₃₀-alkylaryl, and at least one cationic surfactant.
 14. The composition as claimed in claim 13, wherein the weight ratio of metal salt to cationic surfactant is from 9:1 to 1:9. 